Postural Stability Platform

ABSTRACT

Postural stability platforms include at least one movement resistant element Fixed to a base and coupled to a plate. The plate is movable relative to the base but the movement resistant elements resist movement of the plate. Accordingly, subjects standing upon the plate are provided a degree of stability. The movement resistant elements may include springs, hydraulic cylinders, pneumatic cylinders, electromagnetic solenoids, and the like. Furthermore, in certain instances, the degree of resistance offered by a movement resistant element may be adjusted, such as by operation of a valve, so that the stability of the plate upon which the subject stands may vary depending upon the needs of the subject.

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Application60/670,084, filed on Apr. 11, 2005, and entitled BALANCE AND VESTIBULARDISORDER DIAGNOSIS AND REHABILITATION, which is incorporated herein byreference. The present application also claims priority to U.S.Provisional Application 60/719,523, filed on Sep. 22, 2005, and entitledBALANCE AND VESTIBULAR DISORDER DIAGNOSIS AND REHABILITATION, which isalso incorporated herein by reference.

TECHNICAL FIELD

The present application is related to postural stability. Moreparticularly, the present application is related to platforms forassessing and/or rehabilitating postural stability.

BACKGROUND

For various reasons, subjects may have the need to assess and/orrehabilitate their balance. For example, professional athletes may wishto improve their balance in order to improve their performance in theirchosen sport. As another example, subjects suffering from medicalconditions such as vestibular, orthopedic, neuromuscular, orneurological disorders may improve their medical condition throughbalance assessment and rehabilitation.

Attempts have been made to manufacture postural stability platforms.However, these platforms may have drawbacks. For example, theseplatforms include a plate upon which the subject stands. This plate issuspended by an air bladder that is inflated and deflated by an aircompressor. Among other problems that may arise, the air bladder and theair compressor are subject to malfunctions or failure. Furthermore, thesupport provided by the air bladder may be less than ideal.

SUMMARY

Embodiments of the present invention address these issues and others byproviding stability platforms that utilize one or more movementresistant elements such as hydraulic cylinders and/or springs to providestability to the plate upon which the subject stands. Furthermore, incertain embodiments the degree of resistance to movement offered by themovement resistant elements is controllable, such as by a control knobthat controls a position of a valve or other restrictive element thatalters the resistance to movement.

One embodiment is a postural stability platform that includes a base anda plurality of movement resistant elements fixed to the base. Thepostural stability platform further includes a rigid plate coupled tothe movement resistant elements and pivotally coupled to the base suchthat the movement resistant elements resist movement of the platerelative to the base.

Another embodiment is a stability platform that includes a base and atleast one movement resistant element fixed to the base, the at least onemovement resistant element containing a flowing substance. The posturalstability platform further includes a rigid plate coupled to the atleast one movement resistant element and movably coupled to the basesuch that the movement resistant elements resist movement of the platerelative to the base. The postural stability platform also includes avalve having adjustable positions and being in fluid communication withthe at least one movement resistant element such that the position ofthe valve controls the degree of resistance created by the at least onemovement resistant element.

Another embodiment is a postural stability platform that includes a baseand a rigid plate pivotally coupled to the base. The postural stabilityplatform further includes at least one movement resistant element fixedto the base, the at least one movement resistant element having a shaftthat is pivotally coupled to the rigid plate such that the movementresistant element resists movement of the plate relative to the base.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front perspective view of one embodiment of a stabilityplatform.

FIG. 2 shows a rear perspective view of one embodiment of a stabilityplatform.

FIG. 3 shows an exploded view of a center hub of one embodiment.

FIG. 4 shows a partially exploded view of a base of one embodiment.

FIG. 5 shows an exploded view of a cylinder head of the one embodiment.

FIG. 6 shows a cross-sectional view of the cylinder head of oneembodiment.

FIG. 7 shows a cross-sectional view of a center post of one embodiment

FIG. 8 shows an exploded view of a valve control system of oneembodiment.

FIG. 9 shows a schematic of a hydraulic system of one embodiment.

DETAILED DESCRIPTION

Embodiments of postural stability platforms provide one or more movementresistant elements to provide support for the subject standing on abalance plate of the platform. The one or more movement resistantelements may be cylinders that include shafts coupled to the balanceplate. In certain embodiments, multiple movement resistant elements arepresent to provide stability in a number of directions of movement ofthe balance plate. In certain embodiments, one or more adjustable valvesare present so that the adjustment to the valve alters the degree ofresistance to movement.

FIGS. 1 and 2 show one embodiment of a postural stability platform 100.The platform 100 of this example includes many external features. Theplatform 100 includes a base assembly 102 that has a balance plate 104coupled thereto. The balance plate 104 is movable relative to the baseassembly 102 by the balance plate 104 having a pivot point at or nearits center. The details of the pivot point of the balance plate 104 arediscussed in more detail below. The balance plate 104 may include anon-skid sheet to prevent subjects from slipping. An example of such anon-skid sheet is the Safety-Walk® model 370 medium grade non-skid sheetby 3M Co. of St. Paul, Minn. The balance plate 104 of this example maybe made of various rigid materials, such as metal, plastic such asacrylonitrile butadiene styrene (ABS), wood, and so forth. The size ofthe balance plate 104 is a matter of design choice but the diametershould exceed the largest expected foot size so that the foot of asubject can be entirely located atop the balance plate 104.

The base assembly 102 of this particular example includes various otherfeatures as well, such as individual sections 148, top cover plates 149,non-skid sheets 150 applied to the top cover plates 149, and removableplugs 152. The individual sections 148 allow for the base to be easilydisassembled into pieces, transported, and reassembled. These individualsections 148 of this example may be made of similar rigid materials tothe balance plate 104. The top cover plates 149 of this example, whichmay of similar materials to the sections 148, overlap between theindividual sections to help hold the sections together. The non-skidsheet 150 may be included so that a subject does not slip when steppingonto and off of the base assembly 102. The plugs 152 may be included toplug holes provided in the top cover plates 149. The plugs 152 may beremoved so that caster wheel assemblies can be accessed within the baseassembly 102 in order to lower or raise the caster wheel assemblies andeither mobilize or immobilize the stability platform 100.

To provide support, a member 106 is included that is mounted to the baseassembly 102 and extends vertically. The member 106 of this example maybe constructed of a rigid material, such as steel or wood, and isattached within the base assembly 102 to a rigid base discussed below.The member 106 provides a stable point upon which left and right supportrails 112, 114 can attach. The support rails 112, 114 attach to the baseassembly 102 and then extend vertically to attach to a hub 108 mountedatop the member 106. The support rails 112, 114 may be made of variousrigid materials such as metal or wood, and these support rails mayinclude a soft covering such as foam rubber, neoprene, etc. to provide acomfortable hand-hold for a subject to use when stepping onto and off ofthe base assembly 102 and when steadying oneself while standing on thebalance plate 104.

In this example, the hub 108 acts as a point of attachment for thesupport rails 112, 114 and also for a display mast 118. The hub 108 maybe constructed of a rigid material such as metal, wood and so forth andmay have a shell made of ABS or other plastics or similar materials. Amounting bracket 116 is attached to the hub to allow the display mast118 to be mounted in a movable relationship with the hub 108. In thisexample, the mounting bracket 116 swivels within a hole 138 (shown inFIG. 3) of the hub 108. Furthermore, the bracket 116 has the ability torotate forward and backward relative to the hub 106. Thus, a videodisplay device 120, such as a liquid crystal display (LCD) screen, canbe swiveled to be viewed from the front side or the rear side of theplatform 100 and can be rotated forward or backward to improve the angleof viewing. The video display device 120 is attached to the mast 120 viaa mounting bracket 136, which also allows the vertical position of thevideo display device 120 to be altered to adapt to subjects of differentheights.

The video display device 120 of this example may be used for variouspurposes. For example, information about the subject may be displayed. Agraphical user interface may be displayed to allow an operator and/orthe subject to make selections regarding performing various balanceassessment or rehabilitation routines and so forth. Graphical displaysmay then be provided for viewing by the subject while balancing on thebalance plate 104 to produce a response by the subject to thereby assessand/or rehabilitate the balance of the subject.

The stability platform 100 of this particular example is self-containedin that the display 136 as well as corresponding computer equipment isattached to the platform 100. The computer equipment of this embodimentincludes a central processing unit (CPU) 124 held in place by a bracket122 that is attached to the member 106. The CPU 124 is interconnected tothe display device 120 to produce the visual displays for the operatorand subject to view. The CPU 124 is also connected to a printer 128resting on a shelf 126 that is attached to the member 106. The printer128 can be used to print information about the subject and theassessment and/or rehabilitation session.

The CPU 124 is also connected to input devices such as a keyboard 132and mouse 134 that both rest on a shelf 130 that is attached to themember 106. The keyboard 132 and mouse 134 allows the operator and/orsubject to interact with the graphical user interface. Other interfacedevices are applicable as well, such as remote controls that enables theoperator to stand at a distance from the platform and also stand on thefront side of the platform so that both the operator and the subject cansimultaneously view the display device 120.

The CPU 124 may also be connected to a tilt sensor that is mounted tothe balance plate 102. The tilt sensor is discussed in more detailbelow. However, the CPU 124 may receive data from the tilt sensor thatspecifies the attitude of the balance plate 104 such that the CPU maymonitor the movement of the balance plate 104. Thus, the subject may begiven visual feedback of the movement of the balance plate 104 via thedisplay device 120 and this assessment and/or rehabilitation data may bestored for later review or comparison.

In order to accommodate subjects of varying degrees of balance control,the platform 100 of this embodiment includes a mechanism for controllinghow stable the balance plate 104 is. For a subject with very poorbalance, it is likely necessary to assist the subject by providing asignificant amount of stability to the balance plate 104 so that thebalance plate 104 does not make large and sudden changes in positionthat could lead to ineffective assessment and/or rehabilitationsessions.

The mechanism of this example includes a control know 110 mounted uponthe hub 108. As shown in FIG. 3, a center rod 140 passes up through thebottom of the hub 108. This center rod 140 extends down the member 106and into the base where it is then connected to a gear assembly asdiscussed below. At the hub 108, the center rod 140 has a pin 141running perpendicularly through it, and a metal insert 142 fits over therod 140 and couples to the pin 141. A spring 146 and ball 145 arepositioned between the metal insert 142 and a plate 139 having holes143. The knob 110 fits over the metal insert 142 and thereby is coupledto the center rod 140 such that rotation of the knob 110 results inrotation of the center rod 140.

As discussed below, there may be various stability settings that can beselected by the knob 110. To provide for these settings, thespring-biased ball 145 rests in one of the holes 143 of the plate 139.Each hole 143 corresponds to a different stability setting as theycenter rod 140 must be rotated to move the ball 145 from one hole 143 toanother. Markings may be provided on the plate 139 to illustrate thedifferent settings, such as 0-11 plus a lock as the 12^(th) position.Zero indicates a free balance plate 104 having the least stability. Thelock at the 12^(th) position indicates fixed balance plate 104 havingcomplete stability for purposes of stepping onto and off of the balanceplate 104.

As shown in FIG. 4, the base assembly 102 includes the individualsections 148, each having an internal support structure 154 thatincludes holes for receiving the member 106 and for allowing the casterwheel assemblies 174 to be accessed. The torus-like shape of sections148 rests upon and is fixed to a base plate 156.

The base plate 156 includes holes 182 that allow caster wheels 180 to beraised and lowered to immobilize or mobile that platform 100. The casterwheels 180 are suspended by a bracket 176 mounted to the base plate 156and having a bolt 178 threaded into it. The bolt 178 is coupled to thecaster wheel 180 and extends up through the hole of section 148 to beexposed upon removal of the plug 152. Turning the bolt 178 causes thecaster wheel 180 to be raised or lowered.

The stabilization mechanism of this example also includes a set ofmovement resistant elements that are coupled to the base plate 156 andto the balance plate 104. The movement resistant elements may be of manyforms. Some examples include springs, hydraulic cylinders, pneumaticcylinders, electromagnetic solenoids, and the like. As shown in thisexample, there are a set of cylinders 170, 196, 197, and 198. Thesecylinders may be hydraulic or pneumatic in nature. In this example, eachof these cylinders includes a cylinder head 172 which pivotally coupledeach cylinder to a support plate 158. The balance plate 104 is thenmounted to the support plate 158. Examples of the cylinder head 172 anda hydraulic system are discussed in more detail below.

The support plate is suspended over the base plate 156 by a center post199 having a post head assembly 195 that also attached to the supportplate 158. The center post 199 provides a ball and socket type of jointwith the post head assembly 195 as seen in FIG. 7. Thus, the supportplate 158, and hence the balance plate 104, is free to pivot over a 360degree range relative to the base plate 156, and thus relative to theentire base assembly 102. While this example provides for a pivotalconnection of the support plate 158 that allows for a full 360 degreesof movement, the pivotal connection could be limited such as to a singleaxis in other embodiments. For example, the pivotal connection couldrestrict movement to an anterior-posterior axis of rotation of thebalance plate 104, or like wise, a left-right axis of rotation.

In addition to the cylinders 170, 196, 197, and 198, this exampleprovides a spring assembly 160 including springs 166, 168 spaced about aperipheral set of rings 162, 164. The lower ring 164 is mounted via abracket 165 to the base plate 156. The balance plate 104 rests upon theupper ring 162. The springs 166, 168 provide additional movementresistance but once compressed, assist the subject in returning thebalance plate 104 to its neutral position.

As shown, the springs alternate in length with one spring 168 having agreater length that extends from the upper ring 162 to the lower ring164 while adjacent rings 166 have a shorter length such that compressionof the longer spring 168 must take place prior to the shorter adjacentsprings 166 becoming a factor in the movement of the subject. Oneexample of springs are made of stainless steel of a gauge of 2.6millimeters, a pitch of 10 degrees, and an inside diameter of 47millimeters. In one embodiment, the longer spring 168 is 170 millimetersin uncompressed length while the shorter spring 166 is 100 millimetersin uncompressed length.

Additional springs (not shown) may be included such as by placing themnearby the cylinders and coupling them to the base plate 158.Furthermore, skirts (not shown) may be placed on the inside and/oroutside of the rings 162, 164 to help support the springs hold them inplace between the rings 162, 164.

In order to limit the amount of travel of the balance plate 104, posts171 may be included and spaced about the periphery. These posts 171limit the amount of movement possible by the support plate 158. Atorus-like rubber bumper (not shown) may be positioned atop the posts171 to provide 360 degrees of potential contact zones for the supportplate 158.

A tilt sensor 105 is mounted to the support plate 158 so that datasignals are produced that are indicative of the attitude of the balanceplate 104 upon which the subject is standing. As discussed above, acomputer system may receive these data signals and use them to provideimmediate visual feedback to the subject, to compute characteristics ofthe balance capabilities of the subject, and to store for later reviewand analysis. The tilt sensor 105 may be of various types. One exampleis the SQ-SI-360DA Solid-State MEMS Inclinometer by Signal Quest ofLebanon, N.H.

Returning to hydraulic system of this particular example, FIGS. 5 and 6show a cylinder head assembly 172. The hydraulic cylinder 170 has ashaft 171 that extends vertically. Atop the shaft 171 sits a ball 186and socket 184 joint that has external threads. A retaining member 188has two concentric apertures of differing diameters. The smallerdiameter aperture faces the cylinder 170 while the larger diameteraperture faces the support plate 158. The smaller diameter aperture hasa diameter larger than that of the connection of the socket join to theshaft 171.

A first ball bearing 190 that has a diameter smaller than the largediameter aperture but larger than the small diameter aperture sitswithin the large diameter aperture of the retaining member 188. A ballbearing retaining disk 192 has a channel on each side and sits atop thefirst ball bearing 190 with the first ball bearing 190 being positionedwithin the bottom channel. A second ball bearing 194 sits atop the ballbearing retaining disk 192 and is positioned within the top channel. Theretaining disk 192 has a threaded aperture that is tightened upon thethreads of the socket 184. The retaining disk 192 also sits within thelarge diameter aperture of the retaining member 188. The retaining disk192 has a smaller outside diameter than the diameter of the largeaperture of the retaining member 188 which allows the retaining member188 to have 360 degrees of movement relative to the shaft 171.

The retaining member 188 directly attaches to the support plate 158. Indoing so, the top ball bearings 194 contact the underside of the supportplate 158 while the bottom ball bearings contact the retaining member188 to thereby maintain a snug coupling of the shaft 171 to the supportplate 158 while also allowing the support plate 158 to change its anglerelative to the shaft 171 without binding.

Returning to the mechanism for controlling the amount of stabilityprovided to the balance plate 104, the connection of the center rod 140to adjustable valves 202, 204 is shown in FIG. 8. The center rod 140extends down the member 106 until it reaches the interior of theparticular base section 148 upon which the member 106 is mounted. Withinthat particular base section 148, a gearbox assembly 201 is included tointerconnect the center rod 140 to the adjustable valves 202, 204.

In this example, the gearbox includes a large drive gear 240 that iscoupled to the center rod 140 via a ring 238, a washer 242, and a clamp244. Two smaller diameter spur gears 234, 236 are coupled to the shaftsof the valves 204, 202 respectively to thereby provide a gearamplification from the center rod 140 to the valves 202, 204. In oneexample, the large drive gear 240 has a diameter of 102 millimeterswhile the spur gears 234, 236 have a diameter of 18 millimeters. Thecenter rod 140, valves 202, 204, gears 234, 236 are held in place by asupport plate 232 and a mounting bracket 230 that is fixed to the basesection 148.

Thus, rotation of the center rod 140 results in rotation of the controlshafts of the valves 202, 204 to thereby change the degree to which thefluid channel of the valves 202, 204 is open. As the degree of openingincreases, the resistance to the flow of fluid decreases. The resistanceof the flow of the fluid provides the resistance to movement of thebalance plate 104. As discussed above, in one embodiment the controlknob 110 has 12 positions, ranging from completely open valves and afree balance plate 104 to completely closed valves and a fixed balanceplate 104.

FIG. 9 illustrates the hydraulic configuration of this example. It willbe appreciated that there are other configurations possible, involvingeither fewer or more cylinders, fewer or more valves, and so forth. Forexample, there could be a single cylinder used for theanterior-posterior axis and a single cylinder used for the left-rightaxis. It will also be appreciated that the routing of the fluid linesmay be changed. As shown, the top chamber of a cylinder of one axis isin fluid communication with the top chamber of an opposite cylinder ofthe same axis, and the likewise for the bottom chambers. It will beappreciated that the top chamber of a cylinder could instead be in fluidcommunication with a bottom chamber of the same cylinder, especiallywhere a single cylinder is used for a given axis.

In this particular example shown, the valve 202 is located in the fluidpathway between a bottom chamber 208 of cylinder 196 and bottom chamber216 of cylinder 198. This provides resistance in the anterior-posterioraxis of movement. Likewise, the valve 204 is located in the fluidpathway between a bottom chamber 218 of cylinder 197 and a bottomchamber 212 of cylinder 170. This provides resistance in the left-rightaxis of movement. The top chamber 206 of cylinder 196 is in fluidcommunication with the top chamber 214 of cylinder 198 while the topchamber 220 of cylinder 197 is in fluid communication with the topchamber 210 of cylinder 170. The hydraulic hoses 229 that provide thefluid pathways are placed within the base assembly 102 and may be routedbetween the springs 166, 168.

This particular example also includes various three-way connectors 222,224, 226, and 228 that have valves as well. These three-way connectorswith valves allows the hydraulic fluid to be injected into the fluidchannels to fill the hoses 229 each of the chambers of the cylinders170, 196, 197, and 198. One example of such hydraulic fluid is theTellus® 37 weight oil by Shell Oil Co., of Houston, Tex. Pressure gaugesmay be connected to these three-way connectors 222, 224, 226, and 228with valves to pressurize the hydraulic system and to bleed away trappedair within the hydraulic system. For example, the hydraulic system maybe pressurized to 150 pounds per square inch and then the balance plate104 may be worked for about 30 minutes to bleed the air from thehydraulic system.

Examples of the components of the hydraulic system of FIG. 8 includemodel 160S-16SD25N50 hydraulic cylinders by TAIYO LTD of Osaka, Japan.Other examples include model FT1251 proportional valves and highpressure hoses by Kam Kee of Hong Kong.

While the invention has been particularly shown and described withreference to various embodiments thereof, it will be understood by thoseskilled in the art that various other changes in the form and detailsmay be made therein without departing from the spirit and scope of theinvention

1. A stability platform, comprising: a base; a plurality of movementresistant elements fixed to the base; a rigid plate coupled to themovement resistant elements and pivotally coupled to the base such thatthe movement resistant elements resist movement of the plate relative tothe base.
 2. The stability platform of claim 1, wherein the plurality ofmovement resistant elements comprise cylinders.
 3. The stabilityplatform of claim 2, wherein the cylinders are hydraulic cylinders. 4.The stability platform of claim 3, wherein there are at least fourhydraulic cylinders, a first hydraulic cylinder is coupled to a frontportion of the plate, a second hydraulic cylinder is coupled to a rearportion of the plate, a third hydraulic cylinder is coupled to a leftportion of the plate, and a fourth hydraulic cylinder is coupled to aright portion of the base.
 5. The stability platform of claim 4, whereina top chamber of the first hydraulic cylinder is hydraulicallyinterconnected to a top chamber of the second hydraulic cylinder, abottom chamber of the first hydraulic cylinder is hydraulicallyinterconnected to a bottom chamber of the second hydraulic cylinder, atop chamber of the third hydraulic cylinder is hydraulicallyinterconnected to a top chamber of the fourth hydraulic cylinder, abottom chamber of the third hydraulic cylinder is hydraulicallyinterconnected to a bottom chamber of the fourth hydraulic cylinder. 6.The stability platform of claim 5, further comprising: a first valvedisposed within the hydraulic interconnection of the first and secondhydraulic cylinders; and a second valve disposed within the hydraulicinterconnection of the third and fourth hydraulic cylinders.
 7. Thestability platform of claim 6, further comprising: a controlmechanically interconnected to the first and second valves, whereinmanipulation of the control adjusts the degree of opening of the firstand second valves.
 8. The stability platform of claim 1, furthercomprising: a control interconnected to the plurality of movementresistant elements, wherein manipulation of the control adjusts theamount of resistance provided by the plurality of movement resistantelements.
 9. The stability platform of claim 2, wherein the movementresistant elements further comprise springs spaced about the peripheryof the plate.
 10. The stability platform of claim 1, wherein themovement resistant elements comprise springs spaced about the peripheryof the plate.
 11. The stability platform, wherein the base comprises astep adjacent to the plate.
 12. The stability platform of claim 1,further comprising a first vertically elongated member extending upwardfrom the base.
 13. The stability platform of claim 12, furthercomprising first and second rails extending upward from opposing sidesof the base to a top portion of the first vertically elongated member.14. The stability platform of claim 12, further comprising: a hub fixedto the top of the first vertically elongated member; and a secondvertically elongated member extending upward from the top of the firstvertically elongated member, the second vertically elongated memberbeing rotatable about a longitudinal axis in relation to the hub. 15.The stability platform of claim 14, further comprising: a controldisposed on the hub and interconnected to the plurality of movementresistant elements, wherein manipulation of the control adjusts theamount of resistance provided by the plurality of movement resistantelements.
 16. The stability platform of claim 12, further comprising atleast one shelf fixed to the first vertically elongated member.
 17. Thestability platform of claim 16, further comprising: a tilt sensorcoupled to the plate; and a computer located on the at least one shelf,the computer being in electrical communication with the tilt sensor. 18.The stability platform of claim 1, wherein each movement resistantelement includes a shaft with a pivotal connection to the plate.
 19. Thestability platform of claim 18, wherein the pivotal connectioncomprises: a retaining member having a first aperture of a firstdiameter and having a second aperture of a second diameter that isgreater than the first diameter, the apertures being concentric, theshaft of the movement resistant element extending through the first andsecond apertures; first and second ball bearings; and a bearingretaining disk having a disk diameter less than the second diameter andlarger than the first diameter, the retaining disk having a channel oneach side with the first ball bearing seated in one channel of theretaining disk and with the second ball bearing seated in the otherchannel of the retaining disk, the retaining disk being disposed withinthe second aperture and being movable within the second aperture, theretaining disk having a ball and socket joint wherein a socket portionof the ball and socket joint is fixed relative to the retaining diskwhile the ball portion pivots relative to the socket, the ball portionbeing affixed to the shaft of the movement resistant element.
 20. Astability platform, comprising: a base; at least one movement resistantelement fixed to the base, the at least one movement resistant elementcontaining a flowing substance; a rigid plate coupled to the at leastone movement resistant element and pivotally coupled to the base suchthat the movement resistant elements resist movement of the platerelative to the base; and a valve having adjustable positions and beingin fluid communication with the at least one movement resistant elementsuch that the position of the valve controls the degree of resistancecreated by the at least one movement resistant element.
 21. Thestability platform of claim 20, wherein the at least one movementresistant element is a hydraulic cylinder.
 22. The stability platform ofclaim 20, further comprising a control knob mechanically coupled to thevalve such that rotation of the control knob adjusts the position of thevalve.
 23. The stability platform of claim 20, further comprising a tiltsensor coupled to the plate.
 24. The stability platform of claim 20,wherein the at least one movement resistant element has a shaft that hasa pivotal connection to the plate.
 25. The stability platform of claim24, wherein the pivotal connection comprises: a retaining member havinga first aperture of a first diameter and having a second aperture of asecond diameter that is greater than the first diameter, the aperturesbeing concentric, the shaft of the movement resistant element extendingthrough the first and second apertures; first and second ball bearings;and a bearing retaining disk having a disk diameter less than the seconddiameter and larger than the first diameter, the retaining disk having achannel on each side with the first ball bearing seated in one channelof the retaining disk and with the second ball bearing seated in theother channel of the retaining disk, the retaining disk being disposedwithin the second aperture and being movable within the second aperture,the retaining disk having a ball and socket joint wherein a socketportion of the ball and socket joint is fixed relative to the retainingdisk while the ball portion pivots relative to the socket, the ballportion being affixed to the shaft of the movement resistant element.26. A stability platform, comprising: a base; a rigid plate pivotallycoupled to the base; at least one movement resistant element fixed tothe base, the at least one movement resistant element having a shaftthat has a pivotal connection to the rigid plate such that the movementresistant element resists movement of the plate relative to the base.27. The stability platform of claim 26, a valve having adjustablepositions and being in fluid communication with the at least onemovement resistant element such that the position of the valve controlsthe degree of resistance created by the at least one movement resistantelement.
 28. The stability platform of claim 26, wherein the pivotalconnection comprises: a retaining member having a first aperture of afirst diameter and having a second aperture of a second diameter that isgreater than the first diameter, the apertures being concentric, theshaft of the movement resistant element extending through the first andsecond apertures; first and second ball bearings; and a bearingretaining disk having a disk diameter less than the second diameter andlarger than the first diameter, the retaining disk having a channel oneach side with the first ball bearing seated in one channel of theretaining disk and with the second ball bearing seated in the otherchannel of the retaining disk, the retaining disk being disposed withinthe second aperture and being movable within the second aperture, theretaining disk having a ball and socket joint wherein a socket portionof the ball and socket joint is fixed relative to the retaining diskwhile the ball portion pivots relative to the socket, the ball portionbeing affixed to the shaft of the movement resistant element.